Single lever control in twin turbopropeller aircraft

ABSTRACT

Herein provided are methods and systems for controlling operation a first propeller of an aircraft, the first propeller associated with a first engine, the aircraft further comprising a second propeller associated with a second engine. A first requested engine power for the first engine is obtained. A second requested engine power for the second engine is obtained. The first propeller is synchronized with the second propeller by setting a first propeller command for the first propeller based on the first and second requested engine power, and the first propeller command is sent for the first propeller.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of U.S. Provisional PatentApplication No. 62/462,090 filed on Feb. 22, 2017, the contents of whichare hereby incorporated by reference in their entirety.

TECHNICAL FIELD

The present disclosure relates generally to engine control, and, moreparticularly, to engine and propeller control in aircraft.

BACKGROUND OF THE ART

A propeller-driven aircraft powerplant consists of two principal anddistinct components: an engine and a propeller. An engine control systemis used to modulate the power output of the engine, for example bycontrolling fuel flow to the engine. Similarly, a propeller controlsystem is used to modulate the thrust produced by the propeller, forexample by changing a propeller rotational speed and/or a propellerblade pitch. In traditional propeller driven aircraft, each of theengine control system and the propeller control system is operated by apilot or other operator using a respective lever for each of thepowerplant components: thus, a throttle lever is used to set a desiredengine power output, and a condition lever is used to set a desiredpropeller rotational speed and blade pitch angle, thereby modulating thethrust output. In addition, modern turbopropeller driven aircraftoperate the propeller at predefined fixed propeller rotational speeds,optimized to a flight phase of the aircraft.

However, the presence of multiple levers for each principal componentsof each powerplant can lead to additional work load for the pilot,especially in cases where the aircraft has multiple engines, such astwin turbopropeller aircraft.

As such, there is room for improvement.

SUMMARY

In one aspect, there is provided a method for controlling operation afirst propeller of an aircraft, the first propeller associated with afirst engine, the aircraft further comprising a second propellerassociated with a second engine. A first requested engine power for thefirst engine is obtained. A second requested engine power for the secondengine is obtained. The first propeller is synchronized with the secondpropeller by setting a first propeller command for the first propellerbased on the first and second requested engine power, and the firstpropeller command is sent for the first propeller.

In another aspect, there is provided a system for controlling operationof at least a first propeller of an aircraft, the first propellerassociated with a first engine, the aircraft further comprising a secondpropeller associated with a second engine. The system comprises at leastone processing unit and a non-transitory computer-readable memory havingstored thereon program instructions. The program instructions areexecutable by the at least one processing unit for obtaining a firstrequested engine power for the first engine, obtaining a secondrequested engine power for the second engine, synchronizing the firstpropeller with the second propeller by setting a first propeller commandfor the first propeller based on the first and second requested enginepower, and sending the first propeller command for the first propeller.

In a further aspect, there is provided an aircraft subsystem comprisinga first engine, a first propeller, and a first unified control leverassociated with the first engine and the first propeller, a secondengine, a second propeller, and a second unified control leverassociated with the second engine and the second propeller, a firstengine control system configured for controlling the first engine andthe first propeller based on a first command from the first unifiedcontrol lever, and a second engine control system configured forcontrolling the second engine and the second propeller based on a secondcommand from the second unified control lever. At least one of the firstengine control system and the second engine control system is configuredfor synchronizing the first propeller and the second propeller using thefirst command from the first unified control lever and the secondcommand from the second unified control lever.

DESCRIPTION OF THE DRAWINGS

Reference is now made to the accompanying figures in which:

FIG. 1 is a schematic cross-sectional view of an example engine of anaircraft;

FIGS. 2A-D are block diagrams of example powerplant control systemconfigurations;

FIG. 3 is a graphical representation of example requested power andrequested propeller governing speed curves;

FIG. 4 is a flowchart illustrating an example method for controlling theoperation of a propeller of an aircraft in accordance with anembodiment; and

FIG. 5 is a schematic diagram of an example computing system forimplementing the powerplant control systems of FIGS. 2A-D in accordancewith an embodiment.

It will be noted that throughout the appended drawings, like featuresare identified by like reference numerals.

DETAILED DESCRIPTION

With reference to FIG. 1, there is illustrated a turbopropellerpowerplant 100 for an aircraft of a type preferably provided for use insubsonic flight, generally comprising an engine 110 and a propeller 120.The propeller 120 converts rotary motion from a shaft of the engine 110to provide propulsive force for the aircraft, also known as thrust. Thepowerplant 100 of FIG. 1 is a turboprop, but the engine 110 could alsobe any other type of engine mated to a propeller 120, such as a pistonengine, and the like.

Operation of the engine 110 and of the propeller 120 can be regulated bya pilot or other operator by way of various powerplant controls.Traditionally, a turbopropeller driven aircraft is provided with athrottle lever (also referred to as a power lever), which is used toregulate the output power of the engine 110, and a condition lever,which is used to regulate the propeller rotational speed and blade pitchangle thereby modulating thrust produced by the propeller 120. Forinstance, the aircraft can include one throttle lever and one conditionlever per powerplant 100. For example, a twin turbopropeller aircrafthaving two separate powerplants 100 can have two throttle levers and twocondition levers.

The present disclosure considers the use of a unified control lever(UCL) to control both the output power of the engine 110 and the thrustproduced by the propeller 120. With reference to FIG. 2A, a firstpowerplant control system (PCS) 200 ₁ and a second PCS 200 ₂ are shown.PCS 200 ₁, 200 ₂ are configured for controlling operation of aircraftpowerplants 100 ₁ and 100 ₂, respectively, each having an engine 110,160, and a propeller 120, 170. PCS 200 ₁ is configured for receivinginput from a first UCL 202, which is associated with the firstpowerplant 100 ₁, and from a second UCL 204, which is associated withthe second powerplant 100 ₂. Similarly, PCS 200 ₂ is configured forreceiving input from first and second UCLs 202, 204. Optionally, the PCS200 ₁, 200 ₂ are further configured for receiving additional input fromcockpit controls 206.

The UCLs 202, 204 each provide to PCS 200 ₁, 200 ₂ a respective leverposition, for example based on the angle of the lever vis-à-vis apredetermined reference position. In addition, in some embodiments thecockpit controls 206 include buttons, switches, dials, or otherdiscrete-type input mechanisms which may be located on or proximate theUCLs 202, 204 and which can provide additional input to the PCS 200 ₁,200 ₂. For example, the discrete-type input mechanisms can provideinformation regarding the propeller reference speed, fuel on/off,propeller feather/unfeather, and the like. The lever position, andoptionally the additional input from the cockpit controls 206, can beprovided to each one of PCS 200 ₁, 200 ₂ using any suitable signallingprotocol and over any suitable communication medium. In someembodiments, each one of PCS 200 ₁, 200 ₂ receives the lever positionand the additional input via one or more wires, either as a digitalsignal or as an electrical analog signal. In other embodiments, the UCLs202, 204 can communicate the lever position and the cockpit controls 206can communicate the additional input to PCS 200 ₁, 200 ₂ over one ormore wireless transmission protocols. In some embodiments, an aircraftwill have one UCL per engine powerplant.

PCS 200 ₁, 200 ₂ each include an engine controller 210, 260, and apropeller controller 220, 270. The engine controllers 210, 260 areconfigured for receiving the lever positions from each of the UCLs 202,204, and optionally the additional input from the cockpit controls 206.The lever position and the additional input can be transmitted from theUCLs 202, 204 and from the cockpit controls 206 to the engine controller210, 260 in any suitable fashion and using any suitable communicationprotocol. The following discussion focuses on the operation of one ofthe engine controllers, namely engine controller 210, but it should beunderstood that engine controller 260 may be configured to performsimilar operations.

The engine controller 210 is configured for processing the leverpositions for associated UCL 202, and any additional input from thecockpit controls 206, to obtain a requested engine output power for theengine 110. Based on the requested engine output power, the enginecontroller 210 produces an engine control signal which is sent to theassociated engine 110 to control the operation of the engine 110. Insome embodiments, the engine control signal modulates a flow of fuel tothe engine 110. In other embodiments, the engine control signal altersthe operation of a gear system of the engine 110. Still other types ofengine operation control are considered.

The engine controller 210 is further configured for processing the leverposition and any additional input received from the UCL 204 and from thecockpit controls 206 to obtain a requested engine output power for theengine 160. Put differently, the engine controller 210 will process thelever position for both UCLs 202, 204, and optionally the additionalinput from the cockpit controls 206 to obtain two separate requestedengine output power, one for the engine 110 and one for the engine 160.The engine controller 260 may also be configured to obtain the requestedengine output power for the engines 110, 160.

Then, based on the requested engine output power for the engine 160 asderived from UCL 204, the engine controller 210 can determine a firstpropeller command for the propeller 120. For example, the enginecontroller 210 can use a lookup table, an algorithm, or any othersuitable methodology to determine the required rotational speed by thepropeller 120 based on the requested engine output power for the engine160, which in turn can inform the propeller controller 220 on requiredpropeller rotational speed and/or blade pitch angle for the propeller120. In some embodiments, the engine controller 210 determines apropeller governing speed reference via a lookup table or algorithm. Theengine controller 210 determines the propeller governing speed referencefor the propeller 120 to ensure that the propeller governing speedreferences for the propeller 120 and the propeller 170 are synchronized.In some embodiments, synchronization of the propeller governing speedreferences for the propeller 120 and the propeller 170 requires that thepropeller governing speed references are the same for both propellers120, 170. Put differently, the engine controller 210 sets the firstpropeller command for the first propeller 120 to cause the firstpropeller 120 to operate based on the requested power for the secondengine 160, causing the propellers 120, 170 to operate in afollower-leader configuration.

In some embodiments, the selection of the propeller governing speedreferences is a function of the lever position for the UCL 204 which hasa plurality of transition points or “breakpoints” at which requestedpropeller governing speeds change, and optionally of the cockpitcontrols 206. The breakpoints may align with aircraft flight modes orphases, or with certain emergency conditions. For example, in situationswhere one or more propellers are to be secured either via feathering orby shutting down the powerplant(s) associated with the one or morepropellers.

For example, and with reference to FIG. 3, a lookup table 300 can beused to map the requested engine power and/or the propeller thrust to arequested propeller governing speed. A curve 302 shows a relationshipbetween the lever angle for a UCL (horizontal axis) and the requestedpower for an engine (vertical axis), for example the UCL 202 and theengine 110, and a curve 350 shows a relationship between the lever anglefor the UCL (horizontal axis) and the requested propeller governingspeed for a propeller (vertical axis), for example the propeller 120.The curve 302 is aligned with the curve 350, which share a commonhorizontal axis, and points on the curve 302 can be mapped with arelation to points on the curve 350.

For example, a first section 352 of the curve 350 dictates the referencepropeller governing speed 310 between a maximum reverse positionsetpoint 311 and ground idle gate (GI) 312. A second section 353 isimplemented to adjust the reference propeller governing speed betweenthe GI gate and a flight idle gate (FI) detent 313. In this zone, thepropeller control system blade angle is adjusted directly for a smoothtransition and the transition point can vary as a function principallyof forward speed. A third section 354 dictates the reference propellergoverning speed 314 between the FI gate 313 and an intermediate pointbetween a maximum cruise (MCR) set point 315 and a maximum climb (MCL)set point 317. A fourth section 356 dictates the requested propellergoverning speed 316 between the intermediate point between MCR set point315 and MCL set point 317 and an intermediate point between the MCL setpoint 317 and a normal takeoff (NTO) detent 319. A fifth section 358dictates the requested propeller governing speed 318 between theintermediate point between MCL set point 317 and NTO detent 319 and amaximum forward UCL position 320. In some embodiments, an alternatecurve 304 can be followed in case of an unexpected event for one of theengines. Other methods of translating the requested engine power and/orthe propeller thrust are also considered.

Referring again to FIG. 2A, the engine controller 210 is furtherconfigured for sending the first propeller command to the firstpropeller 120. In the embodiment of FIG. 2A, the engine controller 210is configured to send the first propeller command to the propellercontroller 220, which in turn uses the first propeller command tocontrol operation of the propeller 120. For example, the propellercontroller 220 produces a propeller control signal indicative of thefirst propeller command and sends the propeller control signal to thepropeller 120 to alter a propeller blade pitch, a rotational governingspeed, or any other suitable propeller operating condition.

As discussed hereinabove, some or all the functionality which isimplemented by the engine controller 210 may be mirrored by the enginecontroller 260. In some embodiments, the engine controller 260 receivesthe lever positions for the UCL 204 and optionally any additionalinformation from the cockpit controls 206, obtains the requested enginepower for the engine 160, sets a second propeller command for the secondpropeller 170 based on second requested engine power, and sends thesecond propeller command to the second propeller 170, for example viathe propeller controller 270. Since both engine controllers 210, 260perform the same functionality with respect to propeller governing speedreference based on the same inputs, i.e. the input received from the UCL204 and any additional input from the cockpit controls 206, theoperation of the propellers 120, 170 is synchronized. This ensures thateven in the case of a mismatch of requested engine power for the engines110, 160, the operation of the propellers 120, 170 is synchronized,thereby avoiding undesirable propeller speed mismatch for the aircraft.For example, if the UCLs 202, 204 are positioned at different angles,for example by the pilot, leading to different requested engine powerfor the engines 110, 160 and basic propeller governing speed settings,the engine controllers 210, 260 can correct the imbalance by adjustingthe propeller governing speed reference, for example by setting firstand second propeller commands to result in common propeller rotationspeeds for both propellers 120, 170. In some embodiments, thissynchronization can be overridden, for example by a pilot or otheroperator, or by other control systems, for example in emergencysituations.

The synchronization of the operation of the propellers 120, 170 can beperformed in one or more fashions. In some embodiments, if the firstrequested engine power for engine 110 is lower than the second requestedengine power for engine 160 and, for example, if the rotationalgoverning speed for the first propeller 120 is lower than for the secondpropeller 170, the first propeller command is set to increase therotational speed of the propeller 120 to the rotational speed of thepropeller 170. In another embodiment, if the first requested enginepower for engine 110 is lower than the second requested engine power forengine 160 and, for example, if the rotational governing speed for thefirst propeller 120 is lower than for the second propeller 170, thefirst propeller command is set to increase the rotational speed of thepropeller 120 to the rotational speed of the propeller 170. Still othersynchronization techniques are considered. In some embodiments, thesynchronization technique used depends on the requested engine power forthe engines 110, 160, based on propeller thrust for the propellers 120,170, and/or based on any additional input provided by the cockpitcontrols 206.

In some embodiments where the aircraft has additional powerplants beyondthe powerplants 100 ₁, 100 ₂, the PCS 200 ₁, includes oneengine-controller-and-propeller-controller pair for each additionalpowerplant present in the aircraft. In other embodiments, the PCS 200 ₁,includes only the two engine-controller-and-propeller-controller pairs210, 220 and 260, 270, that is to say oneengine-controller-and-propeller-controller pair for each side or wing ofthe aircraft. In still further embodiments, the PCS 200 ₁, includes anysuitable number of engine-controller-and-propeller-controller pairs. Inembodiments where an aircraft has a plurality of powerplants 100 foreach side or wing of the aircraft, a first side can be designated asleader, and the second side is designated as follower, such that thepropellers of the second side are synchronized to match the operation ofthe propellers of the first side. In addition, in some embodiments, eachof the additional powerplants is associated with a respective UCL, suchthat there are an equal number of powerplants and UCLs.

With reference to FIG. 2B, in some embodiments PCS 200 ₃, 200 ₄ areprovided, each including a respective engine controller 212, 262. Theengine controllers 212, 262 are configured to receive the lever positionfrom a respective one of the UCLs 202, 204 and optionally the additionalinput from the cockpit controls 206. In addition, the engine controllers212, 262 are configured for communicating with one-another. For example,if the propeller 120 is the follower to the propeller 170, which is theleader, the engine controller 212 can obtain the requested engine powerfor the engine 110 associated with the propeller 120 from the receivedlever position of the UCL 202, and can communicate with the enginecontroller 262 to obtain the requested propeller governing reference forthe propeller 170. In some embodiments, the engine controller 262 canprovide the requested engine power for the engine 160 to the enginecontroller 212 directly. In other embodiments, the engine controller 262provides the received lever position of the UCL 204 and any otheradditional data to the engine controller 212, which can be used by theengine controller 212 to determine the requested engine power for theengine 160.

With reference to FIG. 2C, in some embodiments PCS 200 ₅, 200 ₆ areprovided, each having a respective unified controller 230, 280. Eachunified controller 230, 280 is configured for implementing thefunctionality of one of the engine controllers 210, 260, and one of thepropeller controllers 220, 270. In embodiments where the propeller 120is the follower to the propeller 170, the unified controller 230 isconfigured to receive the lever positions for the UCLs 202, 204, obtainthe requested engine power for the engines 110, 160, set a firstpropeller command for the first propeller 120 based on the secondrequested engine power, and send the first propeller command to thepropeller 120. The unified controller 280 can implement similarfunctionality for the engine 160 and the propeller 170.

With reference to FIG. 2D, in some embodiments PCS 200 ₇, 200 ₈ areprovided, each having a unified controller 232, 282. Each unifiedcontroller 232, 282 is configured for implementing the functionality ofone of the engine controllers 212, 262, and one of the propellercontrollers 212, 262. The unified controller 232 is configured toreceive the lever position from the UCL 202 and any additionalinformation from the cockpit controls 206, and to communicate with theunified controller 282 to obtain the requested engine power for theengine 160, either directly or based on the lever position and anyadditional information for the UCL 204 this is then used by unifiedcontroller 232 to set the propeller governing speed for propeller 120.

In each of the embodiments of FIGS. 2A-D, the operation of thepropellers 120, 170 is synchronized based on the lever positions of theUCL 204, and any additional inputs provided via the cockpit controls206, to ensure that the various powerplants 110 ₁, 110 ₂ are operatingthe propellers 120, 170 in a synchronized manner. In some embodiments,this is done by ensuring that the same propeller governing speedreference is used for both propellers 120, 170. Additionally, whilepropeller 120 is designated as the follower to propeller 170, which isthe leader, it should be noted that in other embodiments orconfigurations either of the propellers 120, 170 can be designated asthe leader, with the other as the follower.

With reference to FIG. 4, there is shown a flowchart illustrating anexample method 400 for controlling operation of a first propeller of anaircraft. The method 400 can be implemented by the engine controllers210, 212, or by the unified controllers 230, 232 hereinafter referred toas an engine control system, in embodiments where the propeller 120 is afollower to the propeller 170. At step 402, the engine control systemobtains a first requested engine power, for example for the engine 110.The first requested engine power can be obtained from a lever angle of afirst unified control lever, for example the UCL 202. In someembodiments, the engine control system uses a lookup table or algorithmor other technique to translate the lever angle into the requestedengine power.

At step 404, the engine control system obtains a second requested enginepower, for example for the engine 160. The second requested engine powercan be obtained from a lever angle of a second unified control lever,for example the UCL 204. In some embodiments, the engine control systemuses a lookup table or algorithm or other technique to translate thelever angle into the requested engine power. Alternatively, the secondrequested engine power can be obtained from a separate engine controlsystem, for example the engine controllers 260, 262 or the unifiedcontrollers 280, 282, either as a lever angle or as the requested enginepower itself.

At step 406, optionally the engine control system converts the firstrequested engine power to a first propeller thrust. At step 408,optionally the engine control system converts the second requestedengine power to a second propeller thrust. The conversion of the firstand second requested engine power to first and second propeller thrustcan be performed with the use of a lookup table, an algorithm, or anyother suitable technique. In some embodiments, converting the requestedengine power to propeller thrust is based at least in part on additionalinput received from the UCL 202, 204.

At step 410, the engine control system sets a first propeller commandfor a first propeller, for example propeller 120, based on the secondrequested engine power. In particular, the first propeller command isset so as to synchronize the operation of the first propeller with theoperation of a second propeller, for example propeller 170. Thesynchronization of the operation of the first and second propellers 120,170 ensures that undesirable propeller governing speed mismatch areavoided by having both the first and second propellers adjust theirrespective propeller speeds to cause the propellers 120, 170 to rotatein a synchronized fashion. Therefore, even if the first and secondrequested engine power are different, the engine control system cancorrect for the propeller governing speed mismatch by setting anappropriate first propeller command to produce equivalent behaviour forthe first and second propellers.

At step 412, the first propeller command is sent to the first propeller120. The first propeller command can be sent using any suitable meansand any suitable protocol. For example the command can be sent usingfly-by-wire technology and/or fly-by-wireless technology.

With reference to FIG. 5, the method 400 may be implemented by acomputing device 510, comprising a processing unit 512 and a memory 514which has stored therein computer-executable instructions 516. Theprocessing unit 512 may comprise any suitable devices configured toimplement the system 300 such that instructions 516, when executed bythe computing device 510 or other programmable apparatus, may cause thefunctions/acts/steps of the method 400 as described herein to beexecuted. The processing unit 512 may comprise, for example, any type ofgeneral-purpose microprocessor or microcontroller, a digital signalprocessing (DSP) processor, a central processing unit (CPU), anintegrated circuit, a field programmable gate array (FPGA), areconfigurable processor, other suitably programmed or programmablelogic circuits, or any combination thereof.

The memory 514 may comprise any suitable known or other machine-readablestorage medium. The memory 514 may comprise non-transitory computerreadable storage medium, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus, or device, or any suitable combination of the foregoing. Thememory 514 may include a suitable combination of any type of computermemory that is located either internally or externally to device, forexample random-access memory (RAM), read-only memory (ROM), compact discread-only memory (CDROM), electro-optical memory, magneto-opticalmemory, erasable programmable read-only memory (EPROM), andelectrically-erasable programmable read-only memory (EEPROM),Ferroelectric RAM (FRAM) or the like. Memory 514 may comprise anystorage means (e.g., devices) suitable for retrievably storingmachine-readable instructions 516 executable by processing unit 512.

In some embodiments, the computing device 510 can include one or morefull-authority digital engine controls (FADEC), one or more propellerelectronic control (PEC) units, and the like. In some embodiments, theengine controllers 210, 212, 260, 262 are implemented as dual-channelFADECs. In other embodiments, the engine controllers 210, 212, 260, 262are implemented as two separate single-channel FADECs. In still furtherembodiments, one of the engine controllers, for example the enginecontroller 210, is implemented as a dual-channel FADEC, and the otherengine controller, for example the engine controller 260, is implementedas a single-channel FADEC. In such an embodiment, the engine controller260 may be configured to cause the propeller 170 to operate in aparticular default mode, and the engine controller 210 is configured foradjusting the operation of the propeller 120 to synchronize thepropeller 120 with the propeller 170.

Additionally, in some embodiments the propeller controllers 220, 270 areimplemented as dual-channel PECs, or as two single-channel PECs, or anysuitable combination thereof. The unified controllers 230, 232, 280, 282can be implemented as any suitable combination of FADECs, PECs, and/orany other suitable control devices. In some embodiments, the additionalinputs provided by the cockpit controls 206 can be provided via one ormore engine interface cockpit units.

The methods and systems for controlling operation of a first propellerof an aircraft described herein may be implemented in a high levelprocedural or object oriented programming or scripting language, or acombination thereof, to communicate with or assist in the operation of acomputer system, for example the computing device 600. Alternatively,the methods and systems for controlling operation of a first propellerof an aircraft may be implemented in assembly or machine language. Thelanguage may be a compiled or interpreted language. Program code forimplementing the methods and systems for controlling operation of afirst propeller of an aircraft may be stored on a storage media or adevice, for example a ROM, a magnetic disk, an optical disc, a flashdrive, or any other suitable storage media or device. The program codemay be readable by a general or special-purpose programmable computerfor configuring and operating the computer when the storage media ordevice is read by the computer to perform the procedures describedherein. Embodiments of the methods and systems for controlling operationof a first propeller of an aircraft may also be considered to beimplemented by way of a non-transitory computer-readable storage mediumhaving a computer program stored thereon. The computer program maycomprise computer-readable instructions which cause a computer, or insome embodiments the processing unit 512 of the computing device 510, tooperate in a specific and predefined manner to perform the functionsdescribed herein.

Computer-executable instructions may be in many forms, including programmodules, executed by one or more computers or other devices. Generally,program modules include routines, programs, objects, components, datastructures, etc., that perform particular tasks or implement particularabstract data types. Typically the functionality of the program modulesmay be combined or distributed as desired in various embodiments.

The above description is meant to be exemplary only, and one skilled inthe art will recognize that changes may be made to the embodimentsdescribed without departing from the scope of the invention disclosed.Still other modifications which fall within the scope of the presentinvention will be apparent to those skilled in the art, in light of areview of this disclosure.

Various aspects of the methods and systems for controlling operation ofa first propeller of an aircraft may be used alone, in combination, orin a variety of arrangements not specifically discussed in theembodiments described in the foregoing and is therefore not limited inits application to the details and arrangement of components set forthin the foregoing description or illustrated in the drawings. Forexample, aspects described in one embodiment may be combined in anymanner with aspects described in other embodiments. Although particularembodiments have been shown and described, it will be obvious to thoseskilled in the art that changes and modifications may be made withoutdeparting from this invention in its broader aspects. The scope of thefollowing claims should not be limited by the embodiments set forth inthe examples, but should be given the broadest reasonable interpretationconsistent with the description as a whole.

The invention claimed is:
 1. A method for controlling operation of atleast a first propeller of an aircraft, the first propeller associatedwith a first engine, the aircraft further comprising a second propellerassociated with a second engine, the method comprising: obtaining, at afirst engine control system associated with the first propeller, a firstrequested engine power for the first engine; obtaining, at the firstengine control system, a second requested engine power for the secondengine; synchronizing, via the first engine control system, the firstpropeller with the second propeller by setting a first propeller commandfor the first propeller based on the second requested engine power; andsending, via the first engine control system, the first propellercommand for the first propeller.
 2. The method of claim 1, whereinobtaining the first requested engine power comprises receiving a firstthrottle command based on a lever angle for a first throttle leverassociated with the first engine.
 3. The method of claim 2, whereinobtaining the second requested engine power comprises receiving a secondthrottle command based on a lever angle for a second throttle leverassociated with the second engine.
 4. The method of claim 3, wherein thesecond throttle is a second unified control lever also associated withthe second propeller.
 5. The method of claim 2, wherein the firstthrottle is a first unified control lever also associated with the firstpropeller.
 6. The method of claim 1, wherein setting the first propellercommand comprises setting the first propeller command to match a secondpropeller command for the second propeller based on the second requestedengine power.
 7. The method of claim 6, further comprising sending thesecond propeller command for the second propeller.
 8. The method ofclaim 1, wherein the first engine control system comprises an enginecontroller and a propeller controller.
 9. The method of claim 1, whereinthe first propeller is a plurality of first propellers, the first engineis a plurality of first engines, each of the first propellers associatedwith a respective first engine; wherein the second propeller is aplurality of second propellers, the second engine is a plurality ofsecond engines, each of the second propellers associated with arespective second engine; wherein synchronizing the first propeller withthe second propeller comprises synchronizing the plurality of firstpropellers with the plurality of second propellers by setting aplurality of first propeller commands for the plurality of firstpropellers based on the second requested engine power; and sending theplurality of first propeller commands for the plurality of firstpropellers.
 10. A system for controlling operation of at least a firstpropeller of an aircraft, the first propeller associated with a firstengine, the aircraft further comprising a second propeller associatedwith a second engine, the system comprising: at least one processingunit; and a non-transitory computer-readable memory having storedthereon program instructions executable by the at least one processingunit for: obtaining a first requested engine power for the first engine;obtaining a second requested engine power for the second engine;synchronizing the first propeller with the second propeller by setting afirst propeller command for the first propeller based on the secondrequested engine power; and sending the first propeller command for thefirst propeller.
 11. The system of claim 10, wherein obtaining the firstrequested engine power comprises receiving a first throttle commandbased on a lever angle for a first throttle lever associated with thefirst engine.
 12. The system of claim 11, wherein obtaining the secondrequested engine power comprises receiving a second throttle commandbased on a lever angle for a second throttle lever associated with thesecond engine.
 13. The system of claim 12, wherein the second throttleis a second unified control lever also associated with the secondpropeller.
 14. The system of claim 11, wherein the first throttle is afirst unified control lever also associated with the first propeller.15. The system of claim 10, wherein setting the first propeller commandcomprises setting the first propeller command to match a secondpropeller command for the second propeller based on the second requestedengine power.
 16. The system of claim 15, wherein the programinstructions are further executable for sending the second propellercommand for the second propeller.
 17. The system of claim 16, whereinthe at least one processing unit comprises a first processing unitassociated with the first engine and the first propeller and a secondprocessing unit associated with the second engine and the secondpropeller, the first processing unit and the second processing unit eachbeing configured for executing the program instructions.
 18. The systemof claim 10, wherein the first propeller is a plurality of firstpropellers, the first engine is a plurality of first engines, each ofthe first propellers associated with a respective first engine; whereinthe second propeller is a plurality of second propellers, the secondengine is a plurality of second engines, each of the second propellersassociated with a respective second engine; wherein synchronizing thefirst propeller with the second propeller comprises synchronizing theplurality of first propellers with the plurality of second propellers bysetting a plurality of first propeller commands for the plurality offirst propellers based on the second requested engine power; and sendingthe sending the first propeller command comprises sending the pluralityof first propeller commands for the plurality of first propellers. 19.An aircraft subsystem comprising: a first engine, a first propeller, anda first unified control lever associated with the first engine and thefirst propeller; a second engine, a second propeller, and a secondunified control lever associated with the second engine and the secondpropeller; a first engine control system configured for controlling thefirst engine based on a first command from the first unified controllever; and a second engine control system configured for controlling thesecond engine based on a second command from the second unified controllever; wherein the first engine control system is configured forsynchronizing the first propeller with the second propeller using thesecond command from the second unified control lever.